1 files changed, 62 insertions, 0 deletions
diff --git a/libskrift_merge_glyphs.c b/libskrift_merge_glyphs.c
new file mode 100644
index 0000000..548e8fb
--- /dev/null
+++ b/libskrift_merge_glyphs.c
@@ -0,0 +1,62 @@
+/* See LICENSE file for copyright and license details. */
+#include "common.h"
+
+/* TODO How common are grapheme clusters with more than two glyphs? Should we need a variadic version? */
+
+int
+libskrift_merge_glyphs(LIBSKRIFT_CONTEXT *ctx, struct libskrift_glyph *glyph1,
+                       struct libskrift_glyph *glyph2, struct libskrift_glyph **glyphp)
+{
+	int16_t x1a, x1b, x2a, x2b, y1a, y1b, y2a, y2b, x1, x2, y1, y2;
+	size_t width, height, r, c, size = 1, psize = 1;
+	size_t src_off, dest_off, src_linesize, dest_linesize;
+
+	if (ctx->rendering.smoothing == LIBSKRIFT_SUBPIXEL)
+		size = psize = 3;
+
+	x1a = glyph1->x;
+	x1b = glyph2->x;
+	y1a = glyph1->y;
+	y1b = glyph2->y;
+
+	x2a = (int16_t)(x1a + (int16_t)glyph1->width);
+	x2b = (int16_t)(x1b + (int16_t)glyph2->width);
+	y2a = (int16_t)(y1a + (int16_t)glyph1->height);
+	y2b = (int16_t)(y1b + (int16_t)glyph2->height);
+
+	x1 = MIN(x1a, x1b);
+	y1 = MIN(y1a, y1b);
+	x2 = MAX(x2a, x2b);
+	y2 = MAX(y2a, y2b);
+
+	size *= width  = (uint16_t)(x2 - x1);
+	size *= height = (uint16_t)(y2 - y1);
+
+	*glyphp = calloc(1, offsetof(struct libskrift_glyph, image) + size);
+	if (!*glyphp)
+		return -1;
+
+	(*glyphp)->advance = glyph1->advance + glyph2->advance;
+	(*glyphp)->x       = x1;
+	(*glyphp)->y       = y1;
+	(*glyphp)->width   = (uint16_t)width;
+	(*glyphp)->height  = (uint16_t)height;
+	(*glyphp)->size    = size;
+
+	dest_linesize = width * psize;
+
+	src_linesize = glyph1->width * psize;
+	dest_off  = (size_t)(glyph1->y - y1) * dest_linesize;
+	dest_off += (size_t)(glyph1->x - x1) * psize;
+	for (r = src_off = 0; r < glyph1->height; r++, dest_off += dest_linesize, src_off += src_linesize)
+		memcpy(&(*glyphp)->image[dest_off], &glyph1->image[src_off], src_linesize);
+
+	src_linesize = glyph2->width * psize;
+	dest_off  = (size_t)(glyph2->y - y1) * dest_linesize;
+	dest_off += (size_t)(glyph2->x - x1) * psize;
+	for (r = src_off = 0; r < glyph2->height; r++, dest_off += dest_linesize, src_off += src_linesize)
+		for (c = 0; c < src_linesize; c++)
+			(*glyphp)->image[dest_off + c] = MAX((*glyphp)->image[dest_off + c], glyph2->image[src_off + c]);
+
+	return 0;
+}